The present invention is directed to data terminal devices in general and, more particularly, to the keyboard of the terminal devices. Data terminal devices are designed to be operated under the widest possible business conditions without requiring any modification to their structure. Many businesses include a number of different departments, each of which carry out business transactions which are unique to the nature of the business carried out in that department. An example of this is in modern day department stores where a large number of diverse business transactions are carried out. In these instances, it would be desirable to have a data terminal device which can be utilized in any of the departments located in the department store. Prior data terminal devices which have been used in this type of environment have required a different keyboard configuration which corresponds to the type of business or the accounting procedures carried out in the department in which the terminal device is to be used. This requirement has added to the cost of the terminal device and has prevented the use of other terminal devices having a different keyboard configuration in the case of a breakdown of the terminal device in that department. Various devices have been proposed in the prior art to overcome some of these problems. One example is shown in U.S. Pat. No. 2,625,330 issued to K. M. Buckey et al., and which is assigned to the assignee of the present application, the patent disclosing the use of a flexible member which is positioned over the control keys of an accounting machine, the flexible member containing indicia-bearing areas which are located substantially identical with the control keys of the accounting machine to change the classification of the control keys. This type of construction has been found not to work well on those keyboards where the keys are mounted in close proximity to each other, since depression of a portion of the flexible member will normally result in more than one control key being depressed. Other devices found in the prior art include a waterproof auxiliary keyboard which is placed on the keyboard of the terminal device and which prevents the disabling of the terminal device when water or other types of drinks and food have been accidentally spilled on the keyboard. An example of this type of construction is shown in U.S. Pat. No. 4,020,328 issued to W. R. Bradam and assigned to the assignee of the present application. This type of auxiliary keyboard requires the replacement of the entire auxiliary keyboard to change the key classification of the data terminal device. It is obvious that this is an added expense to the overall cost of the data terminal device.
It is therefore the principle object of the present invention to provide an auxiliary keyboard for a data terminal device which will operate under a number of different business environments or accounting procedures without requiring the replacement of the auxiliary keyboard device.
It is another object of this invention to provide an auxiliary keyboard for a data terminal device which is capable of having the number and location of the keys that are operable to be changed to accommodate different business environments.
It is a further object of this invention to provide an auxiliary keyboard which is capable of having the key classification indicia changed.
It is another object of this invention to provide an auxiliary keyboard for use with a data terminal device which is low-cost and capable of being used on a plurality of different data terminal devices.